The present invention generally relates to dishwashers. More specifically, the present invention relates to spray arm arrangements and food soil handling systems for dishwashers.
It is desirable to provide a dishwasher which can effectively wash dishes which are loaded in a wash cavity of the dishwasher, without the dishes having been pre-rinsed to remove food soil. Improvements in dishwashers have led to models which are capable of more adequate removal of heavy food soil. Therefore, dishwasher users have become accustomed to loading dishwashers with dishes which initially have a significant amount of food soil remaining on the dishes, further increasing the demands on dishwasher performance.
During operation of a dishwasher, wash water drains from a basin and is recirculated through a pump. Food particles washed from the dishes are carried by the wash water. A substantial accumulation of such food particles can cause a drain system to clog. Therefore, it is desirable to provide a dishwasher food soil handling system which prevents clogging. In order to prevent such clogging, devices for processing food particles are generally known. For example, U.S. Pat. No. 5,143,306 discloses a dishwasher having rotating knives driven by a motor for scissoring food particles against a grate. Also, U.S. Pat. No. 4,228,962 discloses a dishwasher having a grate which is rotatably driven on a pump shaft against a resilient block.
Hard foreign objects, such as rings, screws, etc., are sometimes accidentally placed inside a dishwasher. These objects can be damaged by a food soil handling device. Likewise, foreign objects or hard food remains such as bones, seeds, etc., can damage a food soil handling device. Therefore, it is desirable to provide a food soil handling system which prevents foreign objects from becoming damaged. Also, it is desirable to provide a food soil handling device which is not itself damaged by loose hard objects present in a dishwasher.
An auxiliary component such as a food soil processing device must be powered. Preferably, such a device is powered by pressure of the wash water exiting a spray arm providing a reaction force which provides the power through a conversion of motion from the rotating spray arm into mechanical motion of the auxiliary device components. Unfortunately, it has been a problem to adequately power auxiliary elements in a dishwasher. More particularly, the torque generated by a traditional spray arm is sometimes insufficient to overcome the frictional resistance of an additional device, or one which provides a significant level of food soil processing.
A traditional dishwasher has a single spray arm rotatably disposed above a bottom wall of the wash cavity. Such a spray arm is caused to rotate by reaction thrust from water exiting through appropriately oriented spray nozzles disposed in the spray arm. A spray arm of this type is incapable of generating adequate torque to power other friction-creating elements. Therefore, it would be desirable to provide a dishwasher spray arm system which provides a substantial amount of torque to power other elements operably connected therewith.
Furthermore, a traditional spray arm has individual nozzles which follow a circular path, the same path being repeated during each revolution. It would be desirable to improve cleaning action by providing a changing spray pattern. Therefore, it would be desirable to provide an improved dishwasher spray arm system which movably directs its nozzles in a changing path.
It is known to provide a dishwasher spray system including multiple rotating spray arms. For example, U.S. Pat. No. 3,667,473 discloses a dishwasher having two small rotating arms mounted on ends of a main carrier arm. Also, U.S. Pat. Nos. 3,496,949 and 3,468,486 disclose dishwashers having one small rotating arm at the end of a main carrier arm. However, in each of these systems, the main arm is freely rotatable and is driven simply by water thrust through nozzles located in the main arm. Therefore, such systems do not create significant torque.